The three Conservative members of parliament (MPs) all support remaining in the European Union. In a stinging letter to Theresa May confirming their resignations, they said the prime minister had pursued a “disastrous” approach to Brexit that they said was being dictated by the extremist right wing and anti-EU fringes in the Conservative party.

The three—Anna Soubry, Sarah Wollaston, and Heidi Allen—will now join eight former Labour lawmakers who sent shockwaves through Westminster when they announced their exit from Jeremy Corbyn’s party in protest at his approach to Brexit and failure to tackle anti-Semitic bullying.

The 11, who will continue to sit in parliament as a new pro-EU block, are going by the name of the Independent Group. They’re now the joint-fourth biggest grouping in the British parliament.

In the letter sent to May, the three former Conservatives said their party had seen a “shift to the right” in the wake of the Brexit vote, and hit out at May for failing to stand up the rabidly anti-EU group of her party known as the European Research Group (ERG) as well as the Democratic Unionist Party (DUP), whose votes May relies on to pass legislation.

“The final straw for us has been this government’s disastrous handling of Brexit,” they wrote. “Following the EU referendum of 2016, no genuine effort was made to build a cross party, let alone a national consensus to deliver Brexit. Instead of seeking to heal the divisions or to tackle the underlying causes of Brexit, the priority was to draw up red lines. The 48 percent were not only sidelined, they were alienated.”

“We find it unconscionable that a party once trusted on the economy, more than any other, is now recklessly marching the country to the cliff edge of no deal. No responsible government should knowingly and deliberately inflict the dire consequences of such a destructive exit on individuals, communities, and businesses and put at risk the prospect of ending austerity.”

May responded that she was “saddened” by the resignations and accepted that Brexit has “been a source of disagreement both in our party and our country for a long time,” meaning that the process of bringing the U.K.’s membership to an end was “never going to be easy.” However, she said implementing Brexit was “the right thing for the country.”

The prime minister wrote: “I am determined that under my leadership the Conservative party will always offer the decent, moderate, and patriotic politics that the people of this country deserve.”

The Independent Group started Monday when an initial seven Labour MPs resigned, saying their party had been “hijacked by the machine politics of the hard left,” and another saying that she’d come to the “sickening conclusion” the party had become “institutionally anti-Semitic.”

The Independent Group welcomed their new MPs, writing: “Both our parties are broken. We are going to change politics for the better.”